1. Field of the Invention
This invention relates to apparatus for delivery of humidified gases therapy and in particular, though not solely to humidified Positive Airway Pressure (PAP) apparatus used in the treatment of Obstructive Sleep Apnea (OSA).
2. Summary of the Prior Art
OSA is a sleep disorder which affects an estimated 5% of the population in which muscles which normally hold the airway open, relax and ultimately collapse, sealing the airway. The sleep pattern of an OSA sufferer is characterised by repeated sequences of snoring, breathing difficulty, lack of breathing, waking with a start and then returning to sleep. Often the sufferer is unaware of this pattern occurring. Sufferers of OSA usually experience daytime drowsiness and irritability due to a lack of good continuous sleep.
In an effort to treat OSA sufferers, a technique known as Continuous Positive Airway Pressure (CPAP) was devised. A CPAP device consists of a gases supply (or blower) with a conduit connected to supply pressurised gases to a patient, usually through a nasal mask. The pressurised air supplied to the patient effectively assists the muscles to keep the patient's airway open, eliminating the typical OSA sleep pattern.
The use of a CPAP system is known to have side effects such as dehydration of the airways and nasal passages which may lead to Rhinitis (inflammation of the nasal passages). The side effects mean that the patient is less likely to comply with his or her CPAP therapy and the therapy itself may cause an increase in nasal resistance as a response to the high air flow, degrading the pressure level applied to the airway and thereby reducing the effectiveness of the therapy. Accordingly, humidified CPAP systems have been developed. One example is described in U.S. Pat. No. 5,537,997 assigned to Respironics Inc. in which a humidifier is incorporated with the CPAP system so that the patient receives humidified gases. Another example is shown in GB 2338420.
While these humidified systems improve patient comfort when properly used, inappropriate setting or lack of activation of the humidifier component of the CPAP system reduces the comfort benefits. It is known that patients or users are prone to failing to use the system where comfort levels are poor, with users frequently failing to comply within a structured regime of treatment.